Casing for a writing instrument and method of manufacturing the same using a dual injection molding

ABSTRACT

A casing for a writing instrument comprises an outer shaft, an inner shaft, and a nib. The outer shaft is formed using dual injection molding. An outer surface of the outer shaft includes a raised hard part and a raised soft part. The inner shaft is formed of a thin-wall tube having an upper end and a lower end, the inner shaft being configured for insertion inside the outer shaft. The inner shaft further includes a fastener protruding on its upper end that engages an upper end of the outer shaft. The nib is configured to engage the lower end of the inner shaft to help secure the inner shaft within the outer shaft. The raised hard or soft parts on the outer surface of the outer shaft may include an oblique loop-shaped part, a strip-shaped part, and/or an arc-shaped part.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/535,465, filed Sep. 26, 2006, which claims priority from ChineseApplication No. 200510106699.0, filed Sep. 26, 2005, the disclosures ofwhich are incorporated by reference herein in their entirety.

BACKGROUND

This present application relates to casings for writing instruments andmethods of manufacturing the same. All forms of writing instruments arecontemplated, including but not limited to pens, such as ball pointpens, felt tip pens, highlighters, etc., and pencils, such as mechanicalpencils.

To increase comfort for holding a pen, it is known to install a softsection where the pen is held by a user. With the advance of dual-colorinjection molding technology, dual-colored penholders are known in thepen-making industry. One example of a penholder for a pen is disclosedin Chinese Patent No. 031208118 which uses a dual-color-shapingtechnology to form hard and soft parts and a pen clip, each having itsown special position. Nevertheless, improvements are still sought in theindustry to increase the comfort and usability of writing instruments.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further exemplified by the embodimentsdescribed in the Detailed Description. This summary is not intended tospecify key features of the claimed subject matter, nor is it intendedto be used as an aid in determining the scope of the claimed subjectmatter.

The technological solutions disclosed in the present application providea casing for a writing instrument and method of manufacturing the samein which a user's comfort and use of the writing instrument is improved.In addition, a casing for a writing instrument as disclosed herein canconform to different people's habits of holding and squeezing thewriting instrument. As a result, one's finger is not tired easily whenwriting.

The technological scheme adopted by this invention to solve theaforesaid problems is as follows:

In one aspect, the present application describes a casing for a writinginstrument, comprising:

-   -   an outer shaft formed using dual injection molding, wherein an        outer surface of the outer shaft includes a raised hard part        formed of a hard material and a raised soft part formed of a        material that is softer than the hard material;    -   an inner shaft formed of a thin-wall tube having an upper end        and a lower end, the inner shaft being configured for insertion        inside the outer shaft and including a fastener protruding on        its upper end that engages an upper end of the outer shaft; and    -   a nib configured to engage the lower end of the inner shaft.

To relieve fatigue on one's finger when writing, the cross section ofthe outer shaft can be designed roughly as a triangle, with an arc thattransitions between each respective angle of the triangle.

In arranging the raised hard part and soft part on the outer shaft, oneof the soft or hard parts can be configured as a basic part for holdingthe writing instrument, while the other of the soft or hard parts can beconfigured to surround the basic hard or soft part.

The surface of the outer shaft may include an oblique loop-shaped hardor soft part that divides the outer shaft into two sections, namely, anupper section and a lower section. The upper section of the outer shaftmay include one or more strip-shaped hard or soft parts disposed on thesurface of the outer shaft. The strip-shaped parts may be distributedsymmetrically on the outer shaft. The lower section of outer shaft mayinclude one or more arc-shaped hard or soft parts disposed on thesurface of the outer shaft. The arc-shaped parts may be configured toextend laterally from one side to the opposing side of the outer shaft.If desired, characters or patterns can be engraved on the surface of thestrip-shaped parts.

To make it easier to carry the writing instrument, the fastenerprotruding on the upper end of the inner shaft can be extended to form aclip for securing the casing of the writing instrument to an externalobject.

To make it easier to manufacture, the tube forming the inner shaft canbe divided into two sections that engage one another at a socket joint.

Furthermore, the outer surface of the inner shaft can be configured toappear as stainless steel. To achieve this goal at a low cost, the innershaft can be made of a plastic electroplate. If desired, characters orpatterns can be printed on the surface of the inner shaft. Additionally,the surface of the inner shaft can be treated with post-treatments, suchas brightening, sub-brightening, and so on.

Compared with existing technology, writing instruments formed of casingsaccording to the present invention have many advantages. For example, inan embodiment where the outer shaft has a raised hard part and a raisedsoft part formed by dual injection molding and the hard part is made ofa transparent material, the inner shaft is revealed on the surface ofthe hard part of the outer shaft. This advantage is enhanced when theinner shaft has a surface effect. Casings for writing instruments formedaccording to the present invention are not only configured with abetter, more comfortable area for holding the writing instrument, butprovide also a unique and pleasant appearance. In addition, the grade ofthe product can be elevated at a low cost.

Techniques disclosed herein can be used for manufacturing casings forvarious writing tools, including but not limited to pens, such as ballpoint pens, felt tip pens, highlighters, etc., and pencils, such asmechanical pencils.

In another aspect, the present application describes a method ofmanufacturing a casing for a writing instrument, comprising:

-   -   forming an outer shaft using dual injection molding, wherein one        step of the injection molding forms a hard part of the outer        shaft, and another step of the injection molding forms a soft        part of the outer shaft, wherein the soft part includes one or        more openings on the outer surface of the outer shaft that        receive protrusions of the hard part at corresponding positions        on the outer shaft;    -   forming an inner shaft for insertion inside the outer shaft,        wherein forming the inner shaft includes forming a fastener that        protrudes from an upper end of the inner shaft and engages an        upper end of the outer shaft; and    -   forming a nib that engages a lower end of the inner shaft to        help secure the inner shaft within the outer shaft.

In one embodiment, the inner shaft may be comprised of an upper sectionand a lower section that are injection molded separately and thenjoined. In another embodiment, the foregoing method may further compriseextending the fastener from the upper end of the inner shaft to form aclip for securing the casing of the writing instrument to an externalobject.

The method may also further comprise forming the protrusions of the hardpart to include an oblique loop-shaped part that divides the hard partinto an upper section and a lower section. The upper section may includeone or more strip-shaped hard parts and the lower section may includeone or more arc-shaped hard parts protruding from the surface of theouter shaft. The strip-shaped parts may be distributed symmetrically onthe upper section, and the arc-shaped parts may be laterally extended onthe lower section from one side of the outer shaft to another side ofthe outer shaft.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates a front elevational view of one embodiment of acasing for a writing instrument manufactured in accordance with thepresent invention;

FIGS. 1A, 1B, and 1C illustrate, in order, the cross sections A-A, B-B,C-C of the casing shown in FIG. 1;

FIG. 2 illustrates a right side elevational view of the casing shown inFIG. 1;

FIG. 3 illustrates a rear elevational view of the casing shown in FIG.1;

FIG. 4 illustrates a vertical section view of the casing shown in FIG.1;

FIG. 5 illustrates a lower front right perspective view of the casingshown in FIG. 1;

FIG. 5A provides an exploded view of an inner shaft, an outer shaft, anda nib that form the casing shown in FIG. 5;

FIG. 5B provides an exploded view of the inner shaft shown in FIG. 5A;

FIG. 5C provides an exploded view of the outer shaft shown in FIG. 5A,comprising hard and soft parts of the casing;

FIG. 6 illustrates a lower front left perspective view of a writinginstrument formed using the casing shown in FIG. 1, wherein the writinginstrument is a push-type ball point pen;

FIG. 7 illustrates a front elevational view of the pen shown in FIG. 6,with shade lines and stippling to indicate surface contours and texture;

FIG. 8 illustrates a vertical section view of the pen shown in FIG. 6;and

FIG. 9 shows an exploded lower front right perspective view ofcomponents forming the pen shown in FIG. 6.

DETAILED DESCRIPTION

The following is a detailed description of an embodiment of a writinginstrument formed using a casing that is manufactured according to thepresent invention. The casing illustrated in FIGS. 1-5 is comprised ofthree parts: an outer shaft 1, an inner shaft 2, and a nib 3.

The outer shaft 1 may be formed using dual injection molding. In theillustrated embodiment, the molding process produces a tube, the crosssection of which may be roughly shaped as a triangle, as shown in FIGS.1A, 1B, and 1C. The sides of the triangle are shaped with an arc thattransitions between each angle of the triangle.

As shown in FIG. 5, and more particularly in FIG. 5C, the outer shaft 1includes a hard part 1A and a soft part 1B. In one embodiment, thematerials used to form the hard part 1A and the soft part 1B may betransparent ebonite resin MBS and maltha resin TPR, respectively. Theouter shaft 1 is shaped twice by injection molding in a dual injectionmolding machine.

In one embodiment, the hard part 1A is molded first. The shape of thegagger of the mold is the shape of the inner surface of the hard part1A. The shape of the cavity of the mold is the shape of the outersurface of the hard part 1A. The hard part 1A thus formed in the firstinjection molding process may be called a half-product. Its shape, asshown in the upper part of FIG. 5C, is a plastic tube, which may betransparent. The hard part 1A, in this embodiment, has a raised obliqueloop-shaped part 1A1 disposed approximately at the middle of the outershaft 1. The oblique loop-shaped part 1A1 divides the outer shaft 1 intoan upper section and a lower section. On the upper section, there areone or more raised strip-shaped parts 1A2. The strip-shaped parts 1A2may be distributed symmetrically. The lower section may include one ormore raised arc-shaped parts 1A3. In the embodiment shown in FIG. 5C,three arc-shaped parts 1A3 are formed on the hard part 1A of the outershaft 1.

In the above embodiment, the soft part 1B of the outer shaft 1 is moldedsecond. This time, the hard part 1A formed in the first injectionmolding process acts as the gagger of the mold, and the shape of thecavity of the mold is the shape of the outer surface of the soft part1B. The soft part 1B may also be called a half product; that is, the twohalf products (hard part 1A and soft part 1B) are molded to form thewhole product. The shape of the soft part 1B formed in the secondinjection molding is shown in the lower part of FIG. 5C. Correspondingopenings 1B1, 1B2, and 1B3 are configured to receive and respectivelysurround the raised oblique loop-shaped part 1A1, the strip-shaped parts1A2, and the arc-shaped parts 1A3 that were formed on the hard part 1A.These openings allow the oblique loop-shaped part 1A1, the strip-shapedpart 1A2, and the arc-shaped parts 1A3 to protrude outward to thesurface of the casing and help secure the later molded soft part 1B tothe first molded hard part 1A. A dual injection molded outer shaft 1 fora writing instrument is thus obtained. In an alternative embodiment, thehard part 1A and the soft part 1B of the outer shaft 1 may be injectionmolded simultaneously. In addition to having a different hardness, thehard part 1A and the soft part 1B may have a different color, ifdesired.

The inner shaft 2 is formed of a thin-wall tube having an upper end anda lower end. The inner shaft 2 is configured to be inserted inside theouter shaft 1 and includes a fastener 2A protruding on its upper end, asshown in FIG. 5A. The fastener 2A engages an upper end of the outershaft 1. To make it easier to carry and more pleasant to eye, thefastener 2A may be configured to further extend from the inner shaft 2to form a clip 2B that helps secure the casing to an external object. Incircumstances where the process of injection molding the long, thin-walltube forming the inner shaft 2 is likely to produce defects, such asdeviation and shrink, a corrective measure may be taken. As shown inFIG. 5B, the inner shaft 2 may be divided into an upper section 21 and alower section 22 that are injection molded separately. The two sections21 and 22 may be configured to engage one another other, preferablyusing a socket joint. As a result, the inner shaft 2 shown in the upperpart of FIG. 5A is formed.

In a further embodiment in which the grade of the writing instrument isimproved, the outer surface of the inner shaft may be configured toappear as stainless steel. To achieve this goal at a low cost, a plasticelectroplate can be used, i.e., an injection molded plastic inner shaft2 is treated with a surface electroplate, e.g., electroplating chromium,nickel, silver, and so on.

In addition to the functions known to a person skilled in the art, thenib 3 in the present application plays a further role in connecting andfixing itself with the outer shaft 1 and the inner shaft 2. On the upperend 3A of the nib 3, there is an outer screw thread, and on the lowerend 2C of the lower section 22 of the inner shaft 2, there is acorresponding inner screw thread. The outer screw thread of the nib 3 isconfigured to engage the inner screw thread of the inner shaft 2 andthus help secure the inner shaft 2 within the outer shaft 1.

FIGS. 6-9 illustrate a push-type ball point pen made with a casing thathas been manufactured in accordance with the present application. Commonparts used in the pen-making industry, such as a refill cartridge 4,refill spring 5, roller 6, pushing wheel 7, pushing spring 8, andpushing head 9, according to the views shown in FIGS. 8 and 9, areinstalled inside the casing to produce the ball point pen. The pentherewith obtains the advantages of the present invention. An outwardappearance of a pen of this type is shown in FIG. 7.

The invention is not necessarily limited to the representative figures.For example, variations below can be freely substituted.

As to transparent hard materials, in addition to transparent MBS,transparent ABS, or any other suitable resins can be used, provided theyare hard enough to maintain an appropriate rigidity for a casingsuitable for a writing instrument. Similarly, in addition to TPR, anyother suitable materials can be used for the soft part 1B, providedtheir hardness is lower than that of the hard materials used for thehard part 1A.

The cross section of the outer shaft 1 is not limited to a triangleshape. Other shapes can also be selected, such as round, rough square,hexagon, and so on.

As to the distribution of the raised hard and soft parts on the surfaceof the outer shaft 1, the hard part 1A can be adopted as the basic partthat surrounds the soft part 1B.

The combination of the shape and position of the inner shaft surface canbe changed freely. Moreover, the materials used to manufacture the innershaft 2 can be metal or partly metal. Alternatively, the inner shaft 2can adopt an integrated scheme in the invention. If desired, the casingmay not include clip 2B protruding from the inner shaft 2.

The color or the surface pattern of the inner shaft 2 can be anydesirable color or pattern. Casings constructed according to the presentinvention are not limited to making push-type ball point pens. As notedearlier, the casing described and claimed herein may be used with othertypes of pens, pencils, and writing tools. Casings constructed accordingto the present invention can also be used in making writing tools havinga cap, wherein the casing is inserted into and removed from the cap.

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A method ofmanufacturing a casing for a writing instrument, comprising: using dualinjection molding, forming an outer shaft that extends substantially thelength of the casing, wherein one step of the injection molding forms ahard part of the outer shaft, and another step of the injection moldingforms a soft part of the outer shaft, wherein the soft part includes oneor more openings on the outer surface of the outer shaft that receiveprotrusions of the hard part at corresponding positions on the outershaft; forming an inner shaft for insertion inside the outer shaft,wherein forming the inner shaft includes forming a fastener thatprotrudes from an upper end of the inner shaft and engages an upper endof the outer shaft when the inner shaft is inserted inside the outershaft; and forming a nib that engages a lower end of the inner shaft andsecures the inner shaft within the outer shaft.
 2. The method of claim1, further comprising extending the fastener outward from the upper endof the inner shaft to form a clip for securing the casing of the writinginstrument to an external object.
 3. The method of claim 2, furthercomprising curving an upper part of the fastener forming the clip todirect the clip toward an outer surface of the outer shaft.
 4. Themethod of claim 1, further comprising forming the outer shaft with across section shaped as a triangle in which a respective arc transitionsbetween each angle of the triangle.
 5. The method of claim 1, furthercomprising forming the protrusions of the hard part to include anoblique loop-shaped part that divides the hard part into an uppersection and a lower section, the upper section including one or morestrip-shaped hard parts protruding from the surface of the outer shaft,and the lower section including one or more arc-shaped hard partsprotruding from the surface of the outer shaft.
 6. The method of claim5, further comprising distributing the strip-shaped parts symmetricallyon the upper section of the outer shaft.
 7. The method of claim 5,further comprising extending the arc-shaped parts laterally from oneside of the outer shaft to another side of the outer shaft.
 8. Themethod of claim 1, further comprising forming a thread on the nib thatengages a corresponding thread on the inner shaft to help secure theinner shaft within the outer shaft.
 9. The method of claim 1, whereinthe steps of forming the hard part of the outer shaft and forming thesoft part of the outer shaft are performed simultaneously.
 10. Themethod of claim 1, wherein the inner shaft is comprised of an uppersection and a lower section that are injection molded separately andthen joined.
 11. The method of claim 1, wherein the fastener thatprotrudes from the upper end of the inner shaft and engages the upperend of the outer shaft is formed integrally with the inner shaft.
 12. Acasing for a writing instrument, comprising: an outer shaft extendingsubstantially the length of the casing formed using dual injectionmolding, wherein one step of the injection molding forms a hard part ofthe outer shaft, and another step of the injection molding forms a softpart of the outer shaft, wherein the soft part includes one or moreopenings on the outer surface of the outer shaft that receiveprotrusions of the hard part at corresponding positions on the outershaft; an inner shaft formed for insertion inside the outer shaft,wherein the inner shaft is formed with a fastener that protrudes from anupper end of the inner shaft and engages an upper end of the outer shaftwhen the inner shaft is inserted inside the outer shaft; and a nibformed to engage a lower end of the inner shaft, wherein the nib securesthe inner shaft within the outer shaft.
 13. The casing of claim 12,wherein the fastener extends outward from the upper end of the innershaft to form a clip for securing the casing of the writing instrumentto an external object.
 14. The casing of claim 13, wherein an upper partof the fastener forming the clip is curved and directs the clip towardan outer surface of the outer shaft.
 15. The casing of claim 12, whereinthe protrusions of the hard part are formed to include an obliqueloop-shaped part that divides the hard part into an upper section and alower section, the upper section including one or more strip-shaped hardparts protruding from the surface of the outer shaft, and the lowersection including one or more arc-shaped hard parts protruding from thesurface of the outer shaft.
 16. The casing of claim 12, wherein a threadon the nib is configured to engage a corresponding thread on the innershaft to help secure the inner shaft within the outer shaft.
 17. Thecasing of claim 12, wherein the fastener is integrally formed with theinner shaft.
 18. A method of manufacturing a casing for a writinginstrument, comprising: forming an outer shaft that extendssubstantially the length of the casing; forming an inner shaft forinsertion inside the outer shaft, wherein forming the inner shaftincludes forming a fastener that protrudes from an upper end of theinner shaft and engages an upper end of the outer shaft when the innershaft is inserted inside the outer shaft; and forming a nib that engagesa lower end of the inner shaft and secures the inner shaft within theouter shaft.
 19. The method of claim 18, wherein the fastener thatprotrudes from the upper end of the inner shaft and engages the upperend of the outer shaft is formed integrally with the inner shaft. 20.The method of claim 19, further comprising forming the fastener toextend outward from the upper end of the inner shaft to form a clip forsecuring the casing of the writing instrument to an external object.